Bis (1, 1-dihydroperfluoroalkyl) amines and salts thereof



BIS(1,1-D1HYDROPERFLUOROALKYL) AMINES AND SALTS THEREOF Donald R. Husted, St. Paul, and Arthur H. Ahlbrecht,

White Bear Township, Ramsey County, Minn., assignors to Minnesota Mining & Manufacturing Company, St. Paul, Minn., a corporation of Delaware No Drawing. Original application July 17, 1953, Serial No. 368,825. Divided and this application June 25, 1954, Serial No. 439,454

3 Claims. (Cl. 260-583) This invention relates to our discovery of new and useful reactive fluorocarbon compounds.

These new compounds are perfluoro secondary amines, and acid salts thereof, which all have in the molecule a single nitrogen atom linked by means of two separate methylene groups to two terminal fluorocarbon groups, at least one of which provides a fluorocarbon chain or tail, and this nitrogen atom is also bonded to a hydrogen atom.

These secondary amines are bis(1,1-dihydroperfiuoroalkyl) amines represented by the generic formula:

RrHzC where R: and R'r are perfluoroalkyl groups (which can be the same or different) containing up to eleven carbon atoms, that is, fully fluorinated alkyl groups consisting solely of carbon and fluorine, having the formula CnFZn-H. At least one (and preferably both) of these perfluoroalkyl groups contains at least three carbon atoms, so that the molecule has a terminal fluorocarbon tail or tails, and this is of critical importance. These fluorocarbon tails are non-polar, highly stable and inert, and both hydrophobic and oleophobic. Thus one of the perfluoroalkyl groups (Rf and Rr) contains from one to eleven carbon atoms and the other contains from three 'to eleven carbon atoms.

fluorobutyric acid. These amines can also be used for making the diamides (bisamides) of unsaturated polybasic acids (such as maleic acid) and of saturated polybasic acids (such as citric acid, sebacic acid, and succinic acid).

The present amine compounds have notable utility as starting compounds for making the novel (N,N-bis(1,1- dihydroperfluoroalkyl) acylamides represented by the generic formula:

RiEZC R'lHrC R where Rr and R: have the same meaning defined above, and R is an aliphatic hydrocarbon or fluorocarbon group containing one to 17 carbon atoms. These compounds contain at least one fluorocarbon tail and have marked surface active properties. While in general it is preferred The acylamide compounds that contain a hydrocarbon acrylamide or methacrylamide group are of especial interest because they provide reactive monomers which show great resistance to hydrolysis and which can be readily polymerized and copolymerized to form stable and useful high polymers having novel properties. The acrylamides have the formula:

RtHzC O and the methacrylamides have the formula:

RfHzO o Polymers and copolymers of these monomers contain fluorocarbon tails that are exposed at the surface of coatings and articles. These tails are highly stable and inert, are non-polar, and are both oleophobic and hydrophobic.

Polymerization readily occurs at moderately elevated temperatures (50 to C.) in the presence of a free radical chain starter such as a peroxide or persulfate catalyst (e. g., benzoyl peroxide or sodium or potassium persulfate). I

The homopolymers show good chemical and thermal stability, and provide flexible and elastic films and coatings that are highly resistant to water, acids, gasoline, oils, greases, and many common organic solvents, and that are stable at elevated temperatures. Utility is indicated for gaskets and for linings for pipes and tanks.

In addition to homopolymers formed solely from the acrylamide and methacrylamide monomers (and heteropolymers formed by copolymerizing a mixture of an acrylamide and a methacrylamide), novel and useful heteropolymers can be made by copolymerizing a mixture of one or more of our monomers and one or more polymerizable monomers of other types which contain an ethylenic linkage (such as ethylene, styrene, acrylonitrile, butadiene, isoprene, vinyl ethers, vinyl esters, acrylates, methacrylates, acrylic acid, methacrylic acid, maleic anhydride, allyl alcohol, and halogenated derivatives of such monomers).

The present compounds are uniquely dilferent in kind from corresponding compounds that contain only one or two carbon atoms in each of the fluorocarbon groups (Rr and Rr). The presence of at least three carbon atoms is essential to provide a perfiuoro chain serving as a fluorocarbon tail capable of imparting the requisite solubility and surface active properties. It is of critical.

importance that each of the fluorocarbon groups be linked to the nitrogen atom by means of a single methylene group (CH2). A hydrocarbon chain consisting of two or more hydrogenated carbon atoms, imparts too much of a hydrocarbon characteristic and spaces the I for dehydrofluorination. However, a single buried methylene group (CH2) linking the nitrogen atom to the fluorocarbon group, serves to impart desirable reaction characteristics and does not prevent the desired fluorocarbon properties when at least one of the methylene groups is united to a fluorocarbon tail. In the preferred compounds, each methylene group links a fluorocarbon tail" to the nitrogen atom; that is, each perfluoroalkyl group (R: andRr) contains 3 to 11 carbon atoms.

The bis(1,1-dihydroperfluoroalkyl) amines can be made by reduction of'the corresponding diperfluoroacylamides, as by using lithium aluminum hydride as the reduction agent:

By reactingthe amineproduct with the anhydride of a monocarboxylic acid, the corresponding N,N-bis(1,1- dihydroperfluoroalkyl) acylamide derivative is formed Instead of using the anhydride of the acid, use can be made of the acid chloride for preparing the amide derivative product:

NH RG] E N-o The following experimental examples illustrate procedures for making thesubjectcompounds and provide further data on their properties.

, Example 1 The apparatus was a 3000 ml. 3-necked flask fitted with a reflux condenser, tight-sleeve stirrer, dropping funnel and gas inlet tube. The apparatus was dried overnight in a 125 C. oven and assembled while hot and with dry nitrogen flowing then and at all times thereafter to completely exclude air (oxygen); a nitrogen flow of 0.5-1 cubic feet per hour being maintained initially.

The flask was charged with 1000rnl. :of anhydrous diethyl ether and then with 24 grams (0.63 mole) of lithium aluminum hydride, LiAlH4, in finely powdered form, with constant stirring which resulted in the powder being fully dissolved in two hours. (This material should be ground and handled only under a nitrogen atmosphere.) The flask was then cooled in an ice bath and addition was made of a solution oflOO ml. of dry ether containing 62 grams of di-n-perfluorobutyramide:

The addition was made slowly at such rate as to maintain a gentle reflux of ether. Stirring'was continued at room temperature for two hours. The flask was then cooled in a Dry Ice bath (mixture of solid-CO2 and acetone) and 80-ml. (1.96 moles) of methyl alcohol was added to destroy the excesslithium aluminum hydride. (The dropping tube was arranged so that the alcohol would fall onthe surfaceofthe liquid and wouldnot strike the wall of the flaskwhere some unreacted LiAlHt may have been deposited, and ether was added to return the liquid to the original level or slightly higher. The use of explosion shields and remote control is recommended.

An increase of nitrogen flow to a rate of at least 1 to 2 cubic feet per hour is desirable at this stage.)

layer removed, and the aqueous layer extracted three times with ether. The ether layer and ether extracts were combined and distilled. The fraction boiling at 137-l39 C. (at 746.5 mm.) was redistilled to yield a fraction having a boiling point of 138.0138.5 C. (at 735.5 mm.), identified as relatively pure normal N,N- bis(l,1dihydroperfluorobutyl) amine: 1

This liquid compound had a refractive index at 25 C. of 1.2965, and a density (grams/cc. at 20 C.) of 1.614. Analysis showed 69.6% fluorine (69.8% calc.) and 3.67% nitrogen (3.67% calc.).

The hydrochloride salt was prepared by the addition of dryhydrogen chloride gas (ECU to an other solution of this amine. The salt was recovered by evaporation of the ether. It was a white solid material having a melting point of 1l8-l22 C. The surface activity of this salt is illustrated by the fact that addition of 1% to a 5% hydrochloric acid solution reduced the surface tension from dynes/cm. to a value of 38 dynes/cm. This salt is ahnost insoluble in concentrated hydrochloric acid; a behavoir that resembles inorganic chloride salts (such as sodium chloride) rather than organic amine salts. The salt is easily split by water at room temperature, as well as by alkaline solutions, to regenerate the secondary amine.

This N,N-bis(Lbdihydroperfluorobutyl) amine compound is only slightly soluble in water and in mineral oil. It is moderately soluble in commercial heptane, petroleum spirits, benzene and trifluoroethanol. It is soluble in acetone, ethyl alcohol, ether, carbon tetrachloride and chloroform.

Its marked surface active properties are readily demonstrated by simple experiments. A clean test tube partly filled with pure water was shaken to wet the wall. A few drops of the amine compound were added and the tube again shaken. This resulted in the solution drawing away from the wall to form a high-angle meniscus.

When the solution was poured out, the tube was left with a dry wall. This efiect was produced by the adsorption of amine molecules on the glass surface, which were oriented with their fluorocarbon tails projecting outwardly to provide a hydrophobic fluorocarbon surface which the solution could not wet.

A glass surface coated with the amine and dried, was found to have an oil-repellent surface, not being wetted by heptane or mineral oil. An oil drop placed on the surface spreads out and then breaks into small droplets leaving the surface dry.

In another experiment, drops of various organic liquid materials were placed on clean glass microscope slides. A drop of the amine compound was added to each such drop and the behavior observed. The materials tested were carbon tetrachloride, chloroform, benzene, mineral spirits, acetone, ethyl alcohol and ether. Addition of the amine caused spreading .of the drop of liquid or film of liquid, followed by contraction of the liquid away from the glass leaving a dry area.

The foregoing surface active efiects are not produced by N,N-bis(1,1-dihydrotrifluoroethyl) amine, since the trifluoromethyl groups do not provide fluorocarbon tails.

ExampleZ This example illustrates the preparation of long chain secondary amines.

The starting compound was diperfluorocapric amide:

(nC9F19CO)2NH having a vacuum boiling point of 176-179" C. (at 7 mm.). It was reduced with lithium aluminum hydride and the It was a white solid compound having a melting point of 85-86 C.

The hydrochloride salt was prepared from a solution in dry ether by passing in hydrogen chloride, and evaporating the reaction mixture. It was a white solid which upon heating to 125-135 C. liberated HCl.

The secondary amine and its salt had even stronger surface active properties than did the butyl amine of Example 1, owing to the presence of the long fluorocarbon chains.

Preparation of the diperfluoroacylamide starting compounds.-The previously described procedure for making the bis(1,1-dihydroperfluoroalkyl) amines involves reduction of corresponding diperfluoroacylamide starting compounds:

These starting compounds can be readily prepared by reacting primary fluorocarbon amides with fluorocarbon acid anhydrides:

The reaction can be conveniently performed by refluxing 6 derivative by fractional distillation. It will be noted that the R: and R'r groups of the product compound will be difierent when the amide and anhydride reactants have correspondingly different fluorocarbon groups.

These diperfluoroacylamide compounds are described and claimed in the companion application of G. H. Smith, S. N. 368,820, filed on July 17, 1953 and since issued as Patent No. 2,701,814 (Feb. 8, 1955). The primary amide starting compounds are described in the Diesslin, Kauck and Simons Patent No. 2,567,011 (Sept. 4, 1951).

We claim:

1. The new and useful compounds of the class consisting of the bis(1,l-dihydroperfluoroalkyl) amines having the formula:

where Rr and R: are perfluoroalkyl groups, one of which contains 1 to 11 carbon atoms and the other contains 3 to 11 carbon atoms; and the strong-acid salts thereof.

2. The bis(1,1-dihydroperfluoroalkyl) amine compounds having the formula:

RiHnC 7 R rHrC where R: and R: are perfluoroalkyl groups that each contain 3 to 11 carbon atoms.

3. The normal N,N-bis(1,1-dihydroperfluorobutyl) amine compound having the formula:

(n-CsFwCHa) 2NH References Cited in the file of this patent UNITED STATES PATENTS Coover, Jr. et al Sept. 12, 1950 Berry July 10, 1951 

1. THE NEW AND USEFUL COMPOUNDS OF THE CLASS CONSISTING OF THE BIS(1,1-DIHYDROPERFLUOROALKYL) AMINES HAVING THE FORMULA: 